Combined supported liquid membrane/strip dispersion process for the removal and recovery of radionuclides and metals

ABSTRACT

The present invention provides a novel process for the removal and recovery of radionuclides from waste waters and process streams. The process of the present invention utilizes a combination of a supported liquid membrane (SLM) and a strip dispersion to improve extraction of the target species while increasing membrane stability and reducing processing costs. Additionally, the invention provides a family of new extractants, alkyl phenylphosphonic acids, for the removal and recovery of radionuclides and/or metals, including the use of the new extractants in the process. The new extractant selectively removes radionuclides and metals from the feed stream to provide a concentrated strip solution of the target species.

FIELD OF THE INVENTION

The present invention relates to the removal and recovery ofradionuclides and metals from feed solutions, such as waste waters andprocess streams, using supported liquid membrane technology.

BACKGROUND OF THE INVENTION

Liquid membranes combine extraction and stripping, which are normallycarried out in two separate steps in conventional processes such assolvent extractions, into one step. A one-step liquid membrane processprovides the maximum driving force for the separation of a targetedspecies, leading to the best clean-up and recovery of the species (W. S.Winston Ho and Kamalesh K. Sirkar, eds., Membrane Handbook, Chapman &Hall, New York, 1992).

There are two types of liquid membranes: (1) supported liquid membranes(SLMs) and (2) emulsion liquid membranes (ELMs). In SLMs, the liquidmembrane phase is the organic liquid imbedded in pores of a microporoussupport, e.g., microporous polypropylene hollow fibers (W. S. Winston Hoand Kamalesh K. Sirkar, eds., Membrane Handbook, Chapman & Hall, NewYork, 1992). When the organic liquid contacts the microporous support,it readily wets the pores of the support, and the SLM is formed.

For the extraction of a target species from a feed solution, theorganic-based SLM is placed between two aqueous solutions—the feedsolution and the strip solution where the SLM acts as a semi-permeablemembrane for the transport of the target species from the feed solutionto the strip solution. The organic liquid in the SLM is immiscible inthe aqueous feed and strip streams and contains an extractant, a diluentwhich is generally an inert organic solvent, and sometimes a modifier.

The use of SLMs to remove radionuclides from aqueous feed solutions hasbeen long pursued in the scientific and industrial community. Nechaev etal. (A. F. Nechaev, V. V. Projaev, V. P. Kapranchik, “Supported LiquidMembranes in Radioactive Waste Treatment Processes: Recent Experienceand Prospective”, in S. Slate, R. Baker, and G. Benda, eds., Proceedingsof Fifth International Conference on Radioactive Waste Management andEnvironmental Remediation, Volume 2, American Society of MechanicalEngineers, New York, 1995) have reported on the experience andprospective of using SLMs in radioactive waste treatment processes, andthe transport of uranyl ion across SLMs has been studied extensively (J.P. Shukla and S. K. Misra, “Uranyl Ion Transport Across Tri-n-butylPhosphate/n-Dodecane Liquid Membranes”, Proceedings of the InternationalSymposium on Uranium Technology, Bhabha Atomic Research Centre, Bombay,India, pp. 939-946, 1991; M. A. Chaudhary, “Separation of Some MetalIons Using Coupled Transport Supported Liquid Membranes”, in H. Javed,H. Pervez, and R. Qadeer, Modern Trends in Contemporary Chemistry,Scientific Information Division PINSTECH, Islamabad, Pakistan, pp.123-131, 1993).

Chiarizia et al. (R. Chiarizia, E. P. Horwitz, and K. M. Hodgson, AnApplication of Supported Liquid Membranes for Removal of InorganicContaminants from Groundwater, DOE Report No. DE92006971, 1991) havereviewed and summarized the results of an investigation on the use ofSLMs for the removal of uranium and some inorganic contaminants,including technetium, from the Hanford site groundwater. Chiarizia (R.Chiarizia, “Application of Supported liquid Membranes for Removal ofNitrate, Technetium (VII) and Chromium (VI) from Groundwater”, J.Membrane Sci., 55, 39-64 (1991)) has described the separation oftechnetium (VII) and uranium (VI) from synthetic Hanford sitegroundwater using SLMs. Dozol et al. (J. F. Dozol, J. Casas, and A.Sastre, “Stability of Flat Sheet Supported Liquid Membranes in theTransport of Radionuclides from Reprocessing Concentrate Solutions”, J.Membrane Sci., 82, 237-246 (1993)) have studied the stability of flatsheet SLMs in the transport of radionuclides.

Recently, Dozol et al. (J. F. Dozol, N. Simon, V. Lamaare, H. Rouquette,S. Eymard, B. Tournois, D. De Marc, and R. M. Macias, “A Solution forCesium Removal from High-Salinity Acidic or Alkaline Liquid Waste: theCrown Calix[4]arenes”, Sep. Sci. Technol., 34, 877-909 (1999)) havedescribed the use of the extractant, Calix[4]arenes monocrown orbiscrown, blocked in 1,3 alternative cone conformation, in SLMs for theremoval of cesium from high-salinity acidic or alkaline liquid waste.Kedari et al. (C. S. Kedari, S. S. Pandit, and A. Ramanujam, “SelectivePermeation of Plutonium (IV) through Supported Liquid MembraneContaining 2-Ethylhexyl 2-Ethylhexyl Phosphonic Acid as Ion Carrier”, J.Membrane Sci., 156, 187-196 (1999)) have studied the selectivepermeation of plutonium (IV) through a SLM containing 2-ethylhexyl2-ethylhexyl phosphonic acid as the ion carrier.

One disadvantage of SLMs is their instability due mainly to loss of themembrane liquid (organic solvent, extractant, and/or modifier) into theaqueous phases on each side of the membrane (A. J. B. Kemperman, D.Bargeman, Th. Van Den Boomgaard, H. Strathmann, “Stability of SupportedLiquid Membranes: State of the Art”, Sep. Sci. Technol., 31, 2733(1996); T. M. Dreher and G. W Stevens, “Instability Mechanisms ofSupported Liquid Membranes”, Sep. Sci. Technol., 33, 835-853 (1998); J.F. Dozol, J. Casas, and A. Sastre, “Stability of Flat Sheet SupportedLiquid Membranes in the Transport of Radionuclides from ReprocessingConcentrate Solutions”, J. Membrane Sci., 82, 237-246 (1993)). The priorart has attempted to solve this problem through the combined use of SLMwith a module containing two set of hollow fibers, i.e., thehollow-fiber contained liquid membrane (W. S. Winston Ho and Kamalesh K.Sirkar, eds., Membrane Handbook, Chapman & Hall, New York, 1992). Inthis configuration with two sets of microporous hollow-fiber membranes,one carries the aqueous feed solution, and the other carries the aqueousstrip solution. The organic phase is contained between the two sets ofhollow fibers by maintaining the aqueous phases at a higher pressurethan the organic phase. The use of the hollow-fiber contained liquidmembrane increases membrane stability, because the liquid membrane maybe continuously replenished. However, this configuration is notadvantageous because it requires mixing two sets of fibers to achieve alow contained liquid membrane thickness.

In ELMs, an emulsion acts as a liquid membrane for the separation of thetarget species from a feed solution. An ELM is created by forming astable emulsion, such as a water-in-oil emulsion, between two immisciblephases, followed by dispersion of the emulsion into a third, continuousphase by agitation for extraction. The membrane phase is the oil phasethat separates the encapsulated, internal aqueous droplets in theemulsion from the external, continuous phase (W. S. Winston Ho andKamalesh K. Sirkar, eds., Membrane Handbook, Chapman & Hall, New York,1992). The species-extracting agent is contained in the membrane phase,and the stripping agent is contained in the internal aqueous droplets.Emulsions formed from these two phases are generally stabilized by useof a surfactant. The external, continuous phase is the feed solutioncontaining the target species. The target species is extracted from theaqueous feed solution into the membrane phase and then stripped into theaqueous droplets in the emulsion. The target species can then berecovered from the internal aqueous phase by breaking the emulsion,typically via electrostatic coalescence, followed by electroplating orprecipitation.

The use of ELMs to remove radionuclides from aqueous feed solutions hasalso been long pursued in the scientific and industrial community. TheELMs for the removal of radionuclides, including strontium, cesium,technetium, and uranium, have been described in detail (W. S. Winston Hoand Kamalesh K. Sirkar, eds., Membrane Handbook, Chapman & Hall, NewYork, 1992). The extraction of strontium with the ELM technique has beeninvestigated (I. Eroglu, R. Kalpakci, and G. Gunduz, “Extraction ofStrontium Ions with Emulsion Liquid Membrane Technique”, J. MembraneSci., 80, 319-325 (1993)).

One disadvantage of ELMs is that the emulsion swells upon prolongedcontact with the feed stream. This swelling causes a reduction in thestripping reagent concentration in the aqueous droplets which reducesstripping efficiency. It also results in dilution of the target speciesthat has been concentrated in the aqueous droplets, resulting in lowerseparation efficiency of the membrane. The swelling further results in areduction in membrane stability by making the membrane thinner. Finally,swelling of the emulsion increases the viscosity of the spent emulsion,making it more difficult to demulsify. A second disadvantage of ELMs ismembrane rupture, resulting in leakage of the contents of the aqueousdroplets into the feed stream and a concomitant reduction of separationefficiency. Raghuraman and Wiencek (B. Raghuraman and J. Wiencek,“Extraction with Emulsion Liquid Membranes in a Hollow-Fiber Contactor”,AIChE J., 39, 1885-1889 (1993)) have described the use of microporoushollow-fiber contactors as an alternative contacting method to directdispersion of ELMs to minimize the membrane swelling and leakage. Thisis due to the fact that the hollow-fiber contactors do not have the highshear rates typically encountered with the agitators used in the directdispersion. Additional disadvantages include the necessary process stepsfor making and breaking the emulsion.

Thus, there is a need in the art for an extraction process whichmaximizes the stability of the SLM membrane, resulting in efficientremoval and recovery of radionuclides from the aqueous feed solutions.

There is also a need in the art for extractants which selectively removea given target species from the feed stream.

SUMMARY OF THE INVENTION

The present invention relates generally to a process for the removal andrecovery of target species from a feed solution using a combinedSLM/strip dispersion. The invention also relates to a new family ofextractants that are useful for the removal and recovery ofradionuclides and metals.

In one embodiment, the present invention relates to a process for theremoval and recovery of one or more radionuclides from a feed solutionwhich comprises the following steps. First, a feed solution containingone or more radionuclides is passed on one side of the SLM embedded in amicroporous support material and treated to remove the radionuclides bythe use of a strip dispersion on the other side of the SLM. The stripdispersion can be formed by dispersing an aqueous strip solution in anorganic liquid, for example, using a mixer. Second, the stripdispersion, or a part of the strip dispersion, is allowed to stand,resulting in separation of the dispersion into two phases: the organicliquid phase and the aqueous strip solution phase containing aconcentrated radionuclide solution.

The continuous organic phase of the strip dispersion readily wets thepores of a microporous support to form a stable SLM. The process of thepresent invention provides a number of operational and economicadvantages over the use of conventional SLMs.

In another embodiment, the present invention relates to a process forthe removal and recovery of one or more metals from a feed solutionwhich comprises the following steps. First, a feed solution containingone or more metals is passed on one side of the SLM embedded in amicroporous support material and treated to remove the metals by the useof a strip dispersion on the other side of the SLM. As described above,the strip dispersion can be formed by dispersing an aqueous stripsolution in an organic liquid, for example, using a mixer. The stripdispersion, or a part of the strip dispersion, is then allowed to stand,resulting in separation of the dispersion into two phases: the organicliquid phase and the aqueous strip solution phase containing aconcentrated metal solution.

In yet another embodiment, the present invention relates to a family ofnew extractants, alkyl phenylphosphonic acids, e.g., 2-butyl-1-octylphenylphosphonic acid (BOPPA) and 2-octyl-1-dodecyl phenylphosphonicacid (C20 ODPPA), which are useful in both conventional SLMs and theprocess of the present invention for the removal and recovery ofradionuclide and/or metal species, also called herein the “targetspecies.” Use of the new extractants result in improved extraction andan increased concentration of the target species in the aqueous stripsolution.

Thus, it is an object of the present invention to provide an SLM processfor the removal and recovery of target species which provides increasedmembrane stability.

It is another object of the invention to provide an SLM process havinghigh flux.

It is yet another object of the present invention to provide an SLMprocess having improved recovery of the target species to provide aconcentrated strip solution.

It is a further object of the invention to provide an SLM process forthe removal and recovery of a target species from a feed solution whichexhibits decreased operation costs and a decreased capital investmentover convention SLM processes.

It is an object of the present invention to provide an SLM process forthe removal and recovery of radionuclides from a to feed solution.

It is another object of the present invention to provide a process forthe removal and recovery of metals from a feed solution.

It is yet another object of the present invention to provide a processfor the removal and recovery of strontium, cesium, technetium, uranium,boron, plutonium, cobalt, or americium from a feed solution.

It is a further object of the invention to provide a process for theremoval and recovery of calcium, magnesium, and/or zinc from a feedsolution.

It is an object of the invention to provide a family of new extractants,alkyl phenylphosphonic acids, for the removal of target species.

It is also an object of the invention to provide the compound2-butyl-1-octyl phenylphosphonic acid (BOPPA) for the removal of targetspecies.

It is another object of the invention to provide the compound2-octyl-1-dodecyl phenylphosphonic acid (C20 ODPPA) for the removal oftarget species.

It is yet another object of the invention to provide a process for theremoval of strontium, cesium, technetium, uranium, boron, plutonium,cobalt, or americium using an alkyl phenylphosphonic acid.

It is another object of the invention to provide a process for theremoval of strontium, cesium, technetium, uranium, boron, plutonium,cobalt, or americium using 2-butyl-1-octyl phenylphosphonic acid(BOPPA).

It is another object of the invention to provide a process for theremoval of strontium, cesium, technetium, uranium, boron, plutonium,cobalt, or americium using 2-octyl-1-dodecyl phenylphosphonic acid (C20ODPPA).

It is another object of the invention to provide a process for theremoval of calcium, magnesium, and/or zinc using an alkylphenylphosphonic acid.

It is another object of the invention to provide a process for theremoval of calcium, magnesium, and/or zinc using 2-butyl-1-octylphenylphosphonic acid (BOPPA).

It is another object of the invention to provide a process for theremoval of calcium, magnesium, and/or zinc using 2-octyl-1-dodecylphenylphosphonic acid (C20 ODPPA).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the combined supported liquidmembrane/strip dispersion of the present invention.

FIG. 2 is an enlarged view of the schematic representation of thecombined supported liquid membrane/strip dispersion of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a process for the removal and recoveryof a target species. These target species include, but are not limitedto, radionuclides, such as strontium, cesium, technetium, uranium,boron, plutonium, cobalt, and americium, and metals, such as calcium,magnesium, and zinc, from a feed solution, such as waste waters orprocess streams. This new process employs a combination of a supportedliquid membrane (SLM) and a strip dispersion.

The present invention also relates to a family of new extractants, alkylphenylphosphonic acids. Examples of preferred alkyl phosphonic acidsinclude, but are not limited to, 2-butyl-1-octyl phenylphosphonic acid(BOPPA) and 2-octyl-1-dodecyl phenylphosphonic acid (C20 ODPPA). Theseextractants are useful in both conventional SLMs and the present processfor the removal and recovery of radionuclides, such as strontium,cesium, plutonium, cobalt, and americium, and metals, such as calcium,magnesium, and zinc. Use of the new extractants results in improvedextraction of the target species from the feed solution and an increasedconcentration of the target species in the aqueous strip solution.

In one embodiment, the present invention relates to a process for theremoval and recovery of one or more radionuclides from a feed solutionwhich comprises the following steps. First, a feed solution containingone or more radionuclides is passed on one side of the SLM embedded in amicroporous support material and treated to remove the radionuclides bythe use of a strip dispersion on the other side of the SLM. The stripdispersion can be formed by dispersing an aqueous strip solution in anorganic liquid, for example, using a mixer. Second, the stripdispersion, or a part of the strip dispersion, is allowed to stand,resulting in separation of the dispersion into two phases: the organicliquid phase and the aqueous strip solution phase containing aconcentrated radionuclide solution.

In another embodiment, the present invention relates to a process forthe removal and recovery of one or more metals from a feed solutionwhich comprises the following steps. First, a feed solution containingone or more metals is passed on one side of the SLM embedded in amicroporous support material and treated to remove the metals by the useof a strip dispersion on the other side of the SLM. As described above,the strip dispersion can be formed by dispersing an aqueous stripsolution in an organic liquid, for example, using a mixer. The stripdispersion, or a part of the strip dispersion, is then allowed to stand,resulting in separation of the dispersion into two phases: the organicliquid phase and the aqueous strip solution phase containing aconcentrated metal solution.

While any SLM configuration may be employed in the process of theinvention, the preferred configuration employs a hollow fiber module asthe liquid membrane microporous support. Such hollow fiber modulesconsist of microporous hollow fibers arranged in a shell-and-tubeconfiguration. In the present invention, the strip dispersion is passedthrough either the shell side of the module or the tube side of themodule, and the aqueous feed solution containing the target species forextraction is passed through the opposing side of the module. The use ofthe hollow fiber system in the combined SLM/strip dispersion processallows continuous replenishment of the strip dispersion as shown in FIG.1, ensuring a stable and continuous operation.

For the purposes of the invention, strip dispersion is defined as amixture of an aqueous phase and an organic phase. The aqueous phase ofthe dispersion comprises an aqueous strip solution, while the organicphase comprises an extractant or extractants in an organic liquid. Thedispersion is formed by the mixing of the aqueous and organic phases asshown in FIG. 1. This combination results in droplets of the aqueousstrip solution in a continuous organic phase. The dispersion ismaintained during the extraction process due to the flow of thedispersion through a membrane module, e.g., a hollow-fiber module. Thecontinuous organic phase of the strip dispersion readily wets thehydrophobic pores of the microporous hollow fibers in the module,forming a stable liquid membrane.

FIG. 2 shows an enlarged view of a schematic representation of the SLMwith strip dispersion of the present invention. A low pressure, P_(a),which is typically less than approximately 2 psi, is applied on the feedsolution side of the SLM. The pressure P_(a) is greater than thepressure, P_(o), on the strip dispersion side of the SLM. Thisdifference in pressure prevents the organic solution of the stripdispersion from passing through the pores to come into the feed solutionside. The dispersed droplets of the aqueous strip solution in a typicalsize of about 80 to about 800 micrometers and are orders of magnitudelarger than the pore size of the microporous support employed for theSLM, which is in the order of approximately 0.03 micrometer. Thus, thesedroplets are retained on the strip dispersion side of the SLM and cannotpass through the pores to go to the feed solution side.

In this SLM/strip dispersion system, there is a constant supply of theorganic membrane solution, i.e. the organic phase of the stripdispersion, into the pores. This constant supply of the organic phaseensures a stable and continuous operation of the SLM. In addition, thedirect contact between the organic and strip phases provides efficientmass transfer for stripping. The organic and strip phases can be mixed,for example, with high-shear mixing, to increase the contact between thetwo phases.

Once removal of the target species is complete, the mixer for the stripdispersion is stopped, and the dispersion is allowed to stand until itseparates into two phases, the organic membrane solution and theconcentrated strip solution. The concentrated strip solution is theproduct of this process.

The feed solution includes, but is not limited to, waste waters orprocess streams containing radionuclides or metals. The to radionuclidesinclude, but are not limited to, strontium, cesium, technetium, uranium,boron, plutonium, cobalt, and americium. The metals include, but are notlimited to, calcium, magnesium, and zinc.

The microporous support employed in the invention is comprised of, forexample, microporous polypropylene, polytetrafluoroethylene,polyethylene, polysulfone, polyethersulfone, polyetheretherketone,polyimide, polyamide, or mixtures thereof. The preferred microporoussupport is microporous polypropylene hollow fibers.

The aqueous portion of the strip dispersion comprises an aqueous acidsolution, such as a mineral acid. Examples of mineral acids useful inthe present invention include, but are not limited to, sulfuric acid(H₂SO₄), hydrochloric acid (HCl), nitric acid (HNO₃), and acetic acid(CH₃COOH). The acid is present in a concentration between about 0.1 Mand about 18 M. The preferred concentration for the acid solution isbetween about 1 M and about 3 M.

The continuous organic liquid phase into which the aqueous stripsolution is dispersed contains an extractant or extractants. Theextractant is capable of extracting the target species contained in thefeed solution. Typical extractants which are known in the art forextraction of species from waste waters or process streams may beemployed in the present strip dispersion. Selection of such extractantsbased upon the specific target species to be extracted is within thelevel of skill in the art.

The organic liquid of the present strip dispersion optionally comprisesa hydrocarbon solvent or mixture. The hydrocarbon solvent or mixture hasa number of carbon atoms per solvent molecule ranging from 6 to 18,preferably from 10 to 14. The hydrocarbon solvent includes, for example,n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, isodecane,isoundecane, isododecane, isotridecane, isotetradecane, isoparaffinichydrocarbon solvent (with a flash point of 92° C., a boiling point of254° C., a viscosity of 3 cp (at 25° C.), and a density of 0.791 g/ml(at 15.6° C.)) or mixtures thereof.

The organic liquid of the present strip dispersion optionally contains amodifier to enhance the complexation and/or stripping of the targetspecies. The modifier can be, for example, an alcohol, a nitrophenylalkyl ether, a trialkyl phosphate or mixtures thereof. The alcohol canbe, for example, hexanol, heptanol, octanol, nonanol, decanol,undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol,hexadecanol, heptadecanol, octadecanol or mixtures thereof. Thenitrophenyl ether can be, for example, o-nitrophenyl octyl ether(o-NPOE), o-nitrophenyl heptyl ether, o-nitrophenyl hexyl ether,o-nitrophenyl pentyl ether (o-NPPE), o-nitrophenyl butyl ether,o-nitrophenyl propyl ether or a mixture thereof. The trialkyl phosphatecan be, for example, tributyl phosphate, tris(2-ethylhexyl)phosphate ormixtures thereof.

The organic liquid of the present strip dispersion comprises about 2% toabout 100% (approximately 0.05M-3M) extractant and about 0% to about 20%modifier in a hydrocarbon solvent or mixture. More preferably, theorganic liquid of the present strip dispersion comprises about 5% toabout 40% extractant and about 1% to about 10% modifier in a hydrocarbonsolvent or mixture. Even more preferably, the organic liquid comprises5% to about 40% extractant and about 1% to about 10% dodecanol in anisoparaffinic hydrocarbon solvent or in n-dodecane. All percentages areby weight unless specified otherwise.

The present invention has several advantages over conventional SLMtechnology. These advantages include increased membrane stability,reduced costs, increased simplicity of operation, improved flux, andimproved recovery of target species concentration.

The present invention provides a constant supply of the organic membranesolution into the pores of the hollow fiber support. This constantsupply results in an SLM which is more stable than conventional SLMs,ensuring stable and continuous operation. This constant supply alsoeliminates the need for recharging membrane modules, which is requiredwith conventional SLMs. Further, it eliminates the need for a second setof membrane modules for use during recharging of the first set ofmembrane modules. Thus, the present invention decreases not onlyoperational costs but also the initial capital investment in the system.The present invention also increases simplicity of the removaloperation.

The present invention provides direct contact between theorganic/extraction phase and aqueous strip phase. Mixing of these phasesprovides an extra mass transfer surface area in addition to the areagiven by the hollow fibers, leading to extremely efficient stripping ofthe target species from the organic phase. This efficient strippingenhances the flux for the extraction of many targeted species, resultingin unexpectedly high flux results as compared with conventional SLMextractions.

The present invention comprises a new type of SLM which providesincreased flexibility of aqueous strip/organic volume ratio. Thisflexibility allows the use of a smaller volume of aqueous strip solutionto obtain a higher concentration of the recovered species in the aqueousstrip solution. The concentrated strip solution is a valuable productfor resale or reuse.

The present invention also encompasses a family of new extractants,alkyl phenylphosphonic acids, which have advantageous properties overprior art extractants. The alkyl group of the alkyl phenylphosphonicacid is paraffinic (saturated) and includes from 6 to 26 carbon atoms.The new alkyl phenylphosphonic acids include 2-butyl-1-octylphenylphosphonic acid (BOPPA; C12 alkyl group), 2-hexyl-1-decylphenylphosphonic acid (C16 alkyl group),2-octyl-1-decyl/2-hexyl-1-dodecyl phenylphosphonic acid (C18 alkylgroup), 2-octyl-1-dodecyl phenylphosphonic acid (C20 ODPPA; C20 alkylgroup), hexyl phenylphosphonic acid (C6 alkyl group), heptylphenylphosphonic acid (C7 alkyl group), octyl phenylphosphonic acid (C8alkyl group), nonyl phenylphosphonic acid (C9 alkyl group), decylphenylphosphonic acid (C10 alkyl group), undecyl phenylphosphonic acid(C11 alkyl group), dodecyl phenylphosphonic acid (C12 alkyl group),tridecyl phenylphosphonic acid (C13 alkyl group), tetradecylphenylphosphonic acid (C14 alkyl group), pentadecyl phenylphosphonicacid (C15 alkyl group), hexadecyl phenylphosphonic acid (C16 alkylgroup), heptadecyl phenylphosphonic acid (C17 alkyl group), octadecylphenylphosphonic acid (C18 alkyl group), nonadecyl phenylphosphonic acid(C19 alkyl group), decadecyl phenylphosphonic acid (C20 alkyl group),undecadecyl phenylphosphonic acid (C21 alkyl group), dodecadecylphenylphosphonic acid (C23 alkyl group), tridecadecyl phenylphosphonicacid (C23 alkyl group), tetrdecadecyl phenylphosphonic acid (C24 alkylgroup), pentadadecyl phenylphosphonic acid (C25 alkyl group),hexadecadecyl phenylphosphonic acid (C26 alkyl group), and mixturesthereof. Preferred alkyl phenylphosphonic acids include BOPPA and (C20ODPPA).

The new extractants are useful for the removal and recovery ofradionuclides, such as strontium, cesium, plutonium, cobalt, andamericium, and metal species, such as calcium, magnesium, and zinc. In apreferred embodiment, the alkyl phenylphosphonic acid is employed as theextractant in the strip dispersion in the process of the invention. Asseen from the examples appended below, the alkyl phenylphosphonic acidhas significantly increases the extraction of strontium from feedsolutions. The new extractant also extends the SLM operation to a lowerpH range to better utilize the available surface area of thehollow-fiber module. For example, for the removal of strontium, the pHhas been reduced from 4.5 to 3.

The alkyl phenylphosphonic acid may be synthesized, for example, byreacting an alcohol containing from 6 to 26 carbon atoms andphenylphosphonyl dichloride in an organic solvent, such as pyridine.Preferred temperatures for the reaction are between about 0 and 10° C.The reaction is quenched by adding concentrated HCl and ice to thereaction mixture, resulting in a solution having a pH of 1. The alkylphenylphosphonic acid can then be extracted from the reaction mixtureusing a solvent, such as toluene. The alkyl phenylphosphonicacid/solvent solution was washed with 1 M HCl solution and dried, forexample, with MgSO₄ to produce a clear solution. The alkylphenylphosphonic acid can then be recovered by evaporating the solventfrom the solution in any manner.

BOPPA may be synthesized, for example, by reacting 2-butyl-1 -octanoland phenylphosphonyl dichloride in an organic solvent. Preferredtemperatures for the reaction are between about 0 and 10° C. Thereaction is quenched by adding concentrated HCl and ice to the reactionmixture, resulting in a solution having a pH of 1. The BOPPA can then beextracted from the reaction mixture using a solvent, such as toluene.The BOPPA/solvent solution was washed with 1 M HCl solution and dried,for example, with MgSO₄ to produce a clear solution. The BOPPA can thenbe recovered by evaporating the solvent from the solution in any manner.The other alkyl phenylphosphonic acids, including 2-hexyl-1-decyl (C16)phenylphosphonic acid, 2-octyl-1-decyl/2-hexyl-1-dodecyl (C18)phenylphosphonic acid, 2-octyl-1-dodecyl (C20) phenylphosphonic acid,can be synthesized in a similar manner.

This invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations upon thescope thereof. To the contrary, it is to be clearly understood thatresort may be had to various other embodiments, modifications, andequivalents thereof which, after reading the description herein, maysuggest themselves to those skilled in the art without departing fromthe spirit of the present invention and/or the scope of the appendedclaims.

EXAMPLES General Procedure

The strip dispersion for each of the following examples was prepared bymixing an aqueous strip solution in a quantity of, for example, 200 ml,and an organic extractant solution (for example, dodecane containing 2wt. % dodecanol and 8 wt. % extractant) in a quantity of, for example,600 ml, in a Fisher brand mixer with a 2-inch diameter, 6-bladed,high-shear impeller at 500 rpm as measured by an Ono Sokki HT-4100tachometer. The mixer was plugged into a varistat to allow foradjustable speed control. The impeller was initially started at 50% ofits full power and the varistat at 80%.

All of the following examples were run in countercurrent fashion withthe feed solution passed through the tube side of the microporouspolypropylene hollow fiber module. The hollow-fiber moldule was 2.5inches in diameter and 8 inches in length, providing a surface area of1.4 m². The process was first started by passing water through thehollow fiber module. The pressures were adjusted to provide a positivepressure on the feed side of the hollow fiber module. Once the pressureswere adjusted and stable, the water was replaced with the feed solution.A positive pressure was maintained on the feed side to prevent theorganic phase in the shell side from passing through the pores of thehollow fibers.

The pressure of the inlet on the shell side was maintained at 1.25 psiand the outlet pressure of the feed side was set at 3.25 psi, thusmaintaining a 2 psi differential between the two sides. In each of theruns, the feed flow was adjusted to give a flow rate of approximately0.84 liter/min at these pressures. The typical feed solution volume forthese experiments was 4 liters.

Samples from the feed solution and the strip dispersion were taken attimed intervals. The strip dispersion samples were allowed to standuntil phase separation occurred. The aqueous phase from the stripdispersion sample was then collected and centrifuged to facilitatecomplete separation. The aqueous phase samples from the strip dispersionsamples and the feed solution samples were then analyzed by inductivelycoupled plasma (ICP) spectrometry.

The flux of a species removed from the feed solution can be defined bythe following formula:${flux} = \frac{V\quad \Delta \quad C}{t\quad A}$

where V is the volume of the feed solution treated; ΔC is theconcentration change in the feed solution; t is the time at which thesample was taken; and A is the membrane surface area. The flux of thespecies was calculated from the above equation.

The mass transfer coefficient k of the species removed from the feedsolution can be defined by the following formula:$k = {\frac{V}{t\quad A}{\ln \left( \frac{C_{o}}{C_{t}} \right)}}$

where C_(o) is the initial concentration of the species in the feedsolution; C_(t) is the concentration of the species in the feed solutionat time t; t is the time; and the rest of the symbols are as definedabove. The mass transfer coefficient k of the species was calculatedfrom the above equation.

Example 1

A fresh solution of 3 M H₂SO₄ was prepared for use as the stripsolution. A strip dispersion was then prepared by mixing together 250 mlof the 3 M H₂SO₄ solution and 750 ml of n-dodecane containing 2%dodecanol and 8% 2-butyl-1-octyl phenylphosphonic acid (BOPPA) asdescribed in the general procedure above. The strip dispersion was fedinto the shell side of a polypropylene hollow fiber module. A feedsolution containing the following metals was passed into the tube sideof the hollow fiber module: strontium (Sr; 5 ppm), calcium (Ca; 80 ppm),magnesium (Mg; 20 ppm), or zinc (Zn; 50 ppm). The pH of the feedsolution was maintained at 3.0+/−0.1 by adding 5 M NaOH as needed.Samples of the feed and strip solutions were collected at timedintervals as described in the general procedure above and analyzed byICP. Fluxes and k values were then calculated and are reported in Tables1 to 4.

The organic phase extracted the Sr and other ions well at pH 3, but thestripping was poor (1-3 ppm). The Mg and Sr were extracted to a similardegree, while Ca was removed after a 15 minute run. Therefore, 1 M HClwas used as the strip solution for Example 2.

TABLE 1 Sr Dispersion Results BOPPA pH ˜3.0 ± 0.1 Strip 3M H₂SO₄ TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 5.45 5 5.03 0.007200.00720 0.0000382 10 1.53 0.001284 3.08 0.02031 0.03343 0.0002336 151.18 0.02440 0.03257 0.0004569 20 2.65 0.00120 0.31 0.02201 0.014850.0006304 25 0.09 0.01839 0.00391 0.0006161 30 3.40 0.00080 0.02 0.015500.00107 0.0006163 40 4.48 0.001157 0 0.01168 0.000202 Div/0!

TABLE 2 Ca Dispersion Results BOPPA pH ˜3.0 ± 0.1 Strip 3M H₂SO₄ TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 87.2 5 32.2 0.9430.943 0.000474 10 578 0.619 5.3 0.702 0.462 0.000864 15 0.00 0.498 0.090#DIV/0! 20 687 0.117 0.00 0.374 0.000 #DIV/0! 25 0.00 0.299 0.0000#DIV/0! 30 701 0.0150 0.00 0.249 0.00000 #DIV/0!

TABLE 3 Mg Dispersion Results BOPPA pH ˜3.0 ± 0.1 Strip 3M H₂SO₄ TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 23.1 5 22.1 0.01710.0171 0.0000211 10 40.6 0.0431 18.2 0.0420 0.0669 0.0000925 15 12.80.0589 0.0926 0.0001676 20 82.7 0.0451 6.1 0.0730 0.115 0.0003553 25 2.20.0715 0.0669 0.0004747 30 140.00 0.06139 0.5 0.0645 0.0292 0.0006837

TABLE 4 Zn Dispersion Results BOPPA pH ˜3.0 ± 0.1 Strip 3M H₂SO₄ TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 52.10 5 11.50 0.69600.6960 0.0007194 10 332.0 0.03554 2.01 0.4293 0.1627 0.0008306 15 0.450.2951 0.0267 0.0007127 20 362.0 0.0321 0.10 0.2229 0.0060 0.0007362 250.04 0.1785 0.0001 0.0004759 30 379.0 0.01821 0.00 0.1489 0 #DIV/0!

Example 2

A fresh solution of 1 M HCl was prepared for use as the strip solution.A strip dispersion was then prepared by mixing together 250 ml of the 1M HCl solution and 750 ml of n-dodecane containing 2% dodecanol and 8%BOPPA as described in the general procedure above. The strip dispersionwas fed into the shell side of a polypropylene hollow fiber module. Afeed solution containing the following metals was passed into the tubeside of the hollow fiber module: strontium (Sr; 5 ppm), calcium (Ca; 80ppm), magnesium (Mg; 20 ppm), or zinc (Zn; 50 ppm). The pH of the feedsolution was maintained at 3.0+/−0.1 by adding 5 M NaOH as needed.Samples of the feed and strip solutions were collected at timedintervals as described in the general procedure above and analyzed byICP. Fluxes and k values were then calculated and are reported in Tables5 to 8. The 1 M HCl strip solution was found to be a better strippingagent than the than 3 M H₂SO₄.

TABLE 5 Sr Dispersion Results BOPPA pH ˜3.0 ± 0.1 Strip 1M HCl TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 5.61 5 4.70 0.015600.01560 0.0000843 10 1.04 0.000759 3.31 0.01971 0.02383 0.0001670 151.98 0.02074 0.02280 0.0002447 20 7.54 0.006864 1.04 0.01959 0.016110.0003066 25 0.56 0.01731 0.00823 0.0002948 30 12.6 0.00542 0.30 0.015180.00453 0.0003036 40 0.77 0.011856 0.001877 0.000321 70 17.6 0.001339 00.012021 0.00066 #DIV/0!

TABLE 6 Ca Dispersion Results BOPPA pH ˜3.0 ± 0.1 Strip 1M HCl TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 89.2 5 29.6 1.0221.022 0.000525 10 559 0.599 4.0 0.730 0.439 0.000955 15 0.0 0.510 0.068#DIV/0! 20 653 0.101 0.0 0.382 0.000 #DIV/0! 25 0.0 0.306 0.0000 #DIV/0!30 669 0.0171 0.0 0.255 0.00000 #DIV/0!

TABLE 7 Mg Dispersion Results BOPPA pH ˜3.0 ± 0.1 1 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 23.4 5 21.4 0.03430.0343 0.0000425 10 40.6 0.0431 17.1 0.0540 0.0737 0.0001068 15 12.70.0611 0.0754 0.0001417 20 82.7 0.0451 8.6 0.0634 0.0702 0.0001856 255.8 0.0603 0.0480 0.0001876 30 140.0 0.06139 3.9 0.0558 0.0326 0.000193940 1.5 0.046929 0.0412 0.000225 70 144 0.001071 0.169 0.028446 0.00400.000173

TABLE 8 Zn Dispersion Results BOPPA pH ˜3.0 ± 0.1 1 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 52.1 5 13.0 0.67030.6703 0.0006611 10 318.0 0.3404 2.60 0.4243 0.1783 0.0007664 15 0.780.2933 0.0313 0.0005764 20 352.0 0.0364 0.28 0.2221 0.00860 0.0004848 250.17 0.1780 0.00189 0.0002404 30 364.0 0.01286 0.16 0.1484 0.000170.0000261 40 0.126 0.111373 0.00059 5.69E−05 70 385.0 0.005625 00.063796 0.00036 #DIV/0!

Example 3

A fresh solution of 3 M HCl was prepared for use as the strip solution.A strip dispersion was then prepared by mixing together 250 ml of the 3M HCl solution and 750 ml of n-dodecane containing 2% dodecanol and 8%BOPPA as described in the general procedure above. The strip dispersionwas fed into the shell side of a polypropylene hollow fiber module. Afeed solution containing the following metals was passed into the tubeside of the hollow fiber module: strontium (Sr; 5 ppm), calcium (Ca; 80ppm), magnesium (Mg; 20 ppm), or zinc (Zn; 50 ppm). The pH of the feedsolution was maintained at 3.0+/−0.1 by adding 5 M NaOH as needed.Samples of the feed and strip solutions were collected at timedintervals as described in the general procedure above and analyzed byICP. Fluxes and k values were then calculated and are reported in Tables9. No obvious improvement was seen using the 3 M HCL strip solution overthe 1 M HCl strip solution.

TABLE 9 Sr 3 M HCl Results BOPPA pH ˜3.0 ± 0.1 Dispersion Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 5.49 5 5.01 0.008230.00823 0.0000436 10 0.78 0.00048 3.19 0.01971 0.03120 0.0002150 15 1.550.02251 0.02811 0.0003437 20 6.61 0.006245 0.65 0.02075 0.015450.0004146 25 0.24 0.01799 0.00696 0.0004678 30 10.7 0.00438 0.08 0.015460.00279 0.0005291 40 0.01 0.011743 0.0006 0.000495 70 13.1 0.000643 00.011764 2.86E−05 #DIV/0!

TABLE 10 Ca Dispersion Results BOPPA pH ˜3.0 ± 0.1 3 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 88.6 5 31.4 0.9810.981 0.000494 10 558 0.598 3.74 0.727 0.474 0.001013 15 0.00 0.5060.064 #DIV/0! 20 620 0.066 0.00 0.380 0.000 #DIV/0! 25 0.00 0.304 0.0000#DIV/0! 30 620 0.0000 0.00 0.253 0.00000 #DIV/0!

TABLE 11 Mg Dispersion Results BOPPA pH ˜3.0 ± 0.1 3 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 25.3 5 24.5 0.01370.0137 0.0000153 10 22.6 0.0239 20.5 0.0411 0.0686 0.0000849 15 13.20.0691 0.1251 0.0002096 20 61.0 0.0411 7.60 0.0759 0.09597 0.0002629 254.33 0.0719 0.0560 0.0002679 30 90.2 0.03129 2.04 0.0665 0.03940.0003584 40 0.65 0.052821 0.0240 0.000272 70 115.0 0.006643 0.220.03071 0.00123 8.6E−05

TABLE 12 Zn Dispersion Results BOPPA pH ˜3.0 ± 0.1 1 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 51.8 5 10.1 0.71490.7149 0.0007785 10 298 0.3189 1.47 0.4314 0.1479 0.0009177 15 0.270.2944 0.0205 0.0008017 20 321 0.0246 0.21 0.2211 0.00102 0.0001249 250.08 0.1773 0.00222 0.0004596 30 328 0.00750 0.23 0.1473 −0.00256######## 40 0.07 0.11085 0.00273 0.000287 70 328 0 0 0.063429 0.00020#DIV/0!

Example 4

A fresh solution of 1 M HCl was prepared for use as the strip solution.A strip dispersion was then prepared by mixing together 250 ml of the 1M HCl solution and 750 ml of n-dodecane containing 2% dodecanol and 8%BOPPA as described in the general procedure above. The strip dispersionwas fed into the shell side of a polypropylene hollow fiber module. Afeed solution containing the following metals was passed into the tubeside of the hollow fiber module: strontium (Sr; 5 ppm), calcium (Ca; 80ppm), magnesium (Mg,; 20 ppm), or zinc (Zn; 50 ppm). The pH of the feedsolution was maintained at 2.5+/−1.0 by adding 5 M NaOH as needed.Samples of the feed and strip solutions were collected at timedintervals as described in the general procedure above and analyzed byICP. Fluxes and k values were then calculated and are reported in Tables13 to 16. The results of the extraction at pH 2.5 was slightly worsethan those at pH 3, but most of the Sr was removed after 70 minutes.

TABLES 13 Sr Dispersion Results BOPPA pH ˜2.5 ± 0.1 1 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 2.5 0 5.42 5 5.19 0.003940.00394 0.0000206 10 4.13 0.00407 4.74 0.00583 0.00771 0.0000432 15 3.750.00954 0.01697 0.0001116 20 5.52 0.001489 3.05 0.01016 0.012000.0000984 25 2.39 0.01039 0.01131 0.0001161 30 7.43 0.00205 1.85 0.010200.00926 0.0001220 40 1.13 0.009193 0.006171 0.000117 70 12.3 0.0013040.322 0.010924 0.002309 0.000299

TABLES 14 Ca Dispersion Results BOPPA pH ˜2.5 ± 0.1 1 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 2.5 0 87.2 5 40.3 0.8040.804 0.000368 10 281 0.301 8.66 0.673 0.542 0.000732 15 0.00 0.4980.148 #DIV/0! 20 350 0.074 0.00 0.374 0.000 #DIV/0! 25 0.00 0.299 0.0000#DIV/0! 30 353 0.0032 0.00 0.249 0.00000 #DIV/0!

TABLE 15 Mg Dispersion Results BOPPA pH ˜2.5 ± 0.1 1 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 2.5 0 26.8 5 26.5 0.00510.0051 0.0000054 10 22.6 0.0239 25.3 0.0129 0.0206 0.0000221 15 22.70.0234 0.0446 0.0000516 20 61.0 0.0411 20.5 0.0270 0.0377 0.0000485 2518.4 0.0288 0.0360 0.0000515 30 90.2 0.03129 16.0 0.0309 0.04110.0000666 40 12.2 0.031286 0.0651 6.46E−05 70 115 0.006643 5.66 0.0258860.00211  6.1E−05

TABLE 16 Zn Dispersion Results BOPPA pH ˜2.5 ± 0.1 1 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 2.5 0 53.8 5 13.2 0.69600.6960 0.0006691 10 187 0.2000 2.36 0.4409 0.1858 0.0008198 15 0.300.3057 0.0352 0.0009759 20 203 0.0171 0.00 0.2306 0.00513 #DIV/0! 250.00 0.1845 0 #DIV/0! 30 206 0.00321 0.00 0.1537 0 #DIV/0! 40 0.000.115286 0 #DIV/0! 70 208 0.000536 0 0.065878 0 #DIV/0!

Example 5 Comparison Between BOPPA and DEHPA

The experimental procedure for this example using di(2-yl-1-hexyl)phosphoric acid (DEHPA) with feed pH 2.5 was similar to that describedin Example 4 except DEHPA was used instead of BOPPA. Fluxes and k valuesfor strontium were calculated and are reported in Table 17. As shown inTable 17, and as compared with the results in Example 4, the strontiumremoval results with DEHPA at feed pH 2.5 were poor and much worse thanthose with BOPPA. In addition, an experiment using DEHPA at feed pH 4.5resulted in the formation of white solid precipitates in the feedsolution, presumably from the formation of a solid complex between DEHPAand zinc in the feed solution. The precipitates blocked the flow of thefeed through the module and stopped the experiment. Therefore, the BOPPAextractant is much better than the DEHPA extractant for the removal ofstrontium.

TABLE 17 Sr Dispersion Results BOPPA pH ˜2.5 ± 0.1 1 M HCl Strip TimeStrip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 2.5 0 5.42 5 5.20 0.003770.00377 0.0000197 10 9.11 0.007520 5.03 0.00334 0.00291 0.0000158 154.86 0.00320 0.00291 0.0000164 20 9.73 0.000531 4.49 0.00399 0.006340.0000377 25 4.21 0.00415 0.00480 0.0000307 30 11.9 0.001860 3.960.00417 0.00429 0.0000292

Example 6

The experimental procedure for this example was the same as thatdescribed in Example 2, except that 2-hexyl-1-decyl phenylphosphonicacid (C16 HDPPA) was used instead of BOPPA. Fluxes and k values forstrontium were calculated and are reported in Table 18. As shown in thistable, the C16 HDPPA extractant removed strontium very well.

TABLE 18 Sr C16 Dispersion Results HDPPA pH ˜3.0 ± 0.1 1 M HCl StripTime Strip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 5.53 10 3.12 0.003344.58 0.00814 0.00814 0.0000449 20 20.30 0.01841 1.79 0.01603 0.023910.0002237 40 39.00 0.00889 0.00 0.01185 0.00767 #DIV/0!

Example 7 Comparison Between C16 HDPPA and C16 DEHPA

The experimental procedure for this example usingdi(2-hexyl-1-decyl)phosphoric acid (C16 DEHPA) was the same as thatdescribed in Examples 2 and 6, except that C16 DEHPA was used instead ofBOPPA or C16 HDPPA. Fluxes and k values for strontium were calculatedand are reported in Table 19. As shown in this table and as comparedwith the results in Example 6, the strontium removal results with C16DEHPA were poor and much worse than those with C16 HDPPA. In addition,the strip dispersion with C16 DEHPA turned into an emulsion, and it wasdifficult to separate into two phases, the organic liquid phase and theaqueous strip phase, upon standing. In other words, the C16 HDPPAextractant was much better than the C16 DEHPA extractant for the removalof strontium.

TABLE 19 Sr C16 Dispersion Results DEHPA pH ˜3.0 ± 0.1 1 M HCl StripTime Strip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m²*hr) (ppm) g/(m²*hr) g/(m²*hr) cm/sec 0 3.0 0 5.53 10 5.04 0.004200.00420 0.0000221 20 4.67 0.00369 0.00317 0.0000182 30 3.44 0.005970.01054 0.0000728 40 8.27 0.00443 1.73 0.00814 0.01466 0.0001637

Example 8

The experimental procedure for this example was the same as thatdescribed in Example 2, except that a mixture of2-hexyl-1-dodecyl/2-octyl-1-decyl phenylphosphonic acids (C18HDPPA/ODPPA) was used instead of BOPPA. Fluxes and k values forstrontium were calculated and are reported in Table 20. As shown in thistable, the C18 HDPPA/ODPPA extractant mixture removed strontium verywell.

TABLE 20 C18 Sr HDPPA/ Dispersion Results ODPPA pH ˜3.0 +/− 0.1 1 M HClStrip Time Strip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH(ppm) g/(m² * hr) (ppm) g/(m² * hr) g/(m² * hr) cm/sec  0 3.0 0 6.26 103.39 0.00363 5.73 0.00454 0.00454 0.0000211 20 26.7 0.02498 1.81 0.019070.03360 0.0002744 30 0.015 0.01784 0.01539 0.0011412 40 49.7 0.012320.00 0.01341 0.00013 #DIV/0!

Example 9

The experimental procedure for this example was the same as thatdescribed in Example 2, except that 2-octyl-1-dodecyl phenylphosphonicacid (C20 ODPPA) was used instead of BOPPA. Fluxes and k values forstrontium were calculated and are reported in Table 21. As shown in thistable, the C20 ODPPA extractant removed strontium very well.

TABLE 21 Sr C20 Dispersion Results ODPPA pH ˜3.0 +/− 0.1 1 M HCl StripTime Strip Strip Flux Feed Ave. Flux Feed Flux k value (mins.) pH (ppm)g/(m² * hr) (ppm) g/(m² * hr) g/(m² * hr) cm/sec  0 3.0 0 5.30 10 4.880.00360 0.00360 0.0000197 20 3.06 0.00960 0.01560 0.0001111 30 0.320.01423 0.02349 0.0005376 40 28.00 0.00750 0.00 0.01136 0.00274 #DIV/0!

Example 10 Radioactive Strontium-90 Experiments

A series of ten experiments using the combined supported liquid membrane(SLM)/strip dispersion process of the present invention were carried outby the use of radioactive strontium-90. For these experiments, theexperimental procedure and conditions were similar to those describedearlier in the general procedure except those noted below specifically.The following paragraphs describe the EXPERIMENTS, RESULTS, andCONCLUSIONS.

Experiments

Two separate organic solutions were used in the experiments. The firstorganic solution was freshly prepared with a composition of 8 wt % C20ODPPA, 2 wt % dodecanol, and 90 wt % dodecane (42.6 g of C20 ODPPA),which was used in Experiments #1, 2, 3, and 4 with a low feedconcentration of 317 pico Curie per liter (pCi/L) strontium-90 andExperiment #9 with a low feed concentration of 1,000 pCi/L. Thissolution was also used later in Experiment #10 with a high feedconcentration of 487,000 pCi/L Sr-90. The second organic solution usedfor Experiments #5 and 6 with a low feed concentration of 1,000 pC/LSr-90 and for Experiments #7 and 8 with a high feed concentration of27,941 pCi/L was made from two used solutions of the same compositionemployed in Experiments #1, 2, 3, 4, and 9 with the low feedconcentrations.

The strip dispersions were made up of 1.0 M HCl and the previouslymentioned organic solutions. The total strip dispersion volume used wasabout 1 L (0.25 L acid strip solution and 0.75 L organic solution),except for Experiments #7, 8, and 10 where 0.6 L was used (#7 and 8 with0.1 L acid strip solution and 0.5 L organic solution, #10 with 0.040 Lacid solution and 0.560 L organic solution). A fresh acid strip solutionwas used for each experiment.

All of the feed solutions were run at a pH of 3.0. The pH was maintainedbetween 2.9 and 3.0 by the addition of 5.0 M NaOH. Four different feedsolutions were used. As mentioned, Experiments #1-4 used a feed solutionof 317 pCi/L. Experiments #5, 6, and 9 used a feed solution of 1,000pCi/L. Experiments #7 and 8 used a feed solution of about 27,941 pCi/L.Experiment #10 used a feed solution of about 487,000 pCi/L. All of theruns except Experiment #10 used two liters of feed solution. Experiment#10 used one liter of feed. All of the runs used ground water. Theaqueous feed solutions for Experiments #4, 6, 8, and 9 had calcium,magnesium, and zinc added to them to make their concentrations of about80 ppm, 20 ppm, and 50 ppm, respectively.

For these experiments, the feed outlet pressure was maintained between4-4.5 psi, and the strip dispersion inlet pressure was maintainedbetween 1-2 psi. The feed inlet pressure was maintained between 5-5.5psi.

Samples were taken during the experiments from the discharge of themodule and not from the bulk solution. The sample volumes taken were atleast 100 mL. Two strip samples were analyzed after diluting the sample1:100. The strontium-90 concentrations were measured by filtering thesample through 3M's EMPORE® filter paper, which selectively traps about97% of Sr-90. The samples were prepared in the following manner per themanufacturer's directions. Concentrated nitric acid was added to thesample to make a 2.0 N nitric acid solution. The sample was then stirredand allowed to sit. One of the filter papers was placed in a filtersupport and conditioned with 10 mL of methanol for approximately 1minute. After one minute, the methanol was pulled through the filter,followed immediately by 20 mL of 2.0 M HNO₃. Immediately following thenitric acid, the sample was added to the filter. The directions calledfor the sample to be passed through the filter at a rate of about 50mL/min. Most of the samples were passed through the filter at no morethan 25 mL/min; this ensured the capture of Sr-90 by the filter. Thesample was immediately followed by 20 mL of 2.0 M HNO₃. The filter wasthen dried under a heat lamp and was analyzed by a gas flow proportionalcounter, Tennelec 1000 series, Low Background Alpha/Beta CountingSystem. Due to a limited number of filters and the expense of eachfilter, only selected samples were analyzed.

Results

Low Feed Concentration Experiments

Experiments #1, 2, and 3 were all done using the same parameters and 317pCi/L Sr-90 starting concentration. In all of these experiments, thetarget concentration of below 8 pCi/L in the treated ground water wasachieved. In Experiment #4 with calcium, magnesium, and zinc added tothe feed water, the Sr-90 was reduced to below the target concentrationwithin four hours. The data from these experiments along with all of therest of the ten experiments are shown in Table 22 at the end of thisexample. Also included in this table are the mass transfer coefficient kvalues determined from all of the experiments.

Three experiments using the C20 ODPPA extractant were done using astarting Sr-90 concentration of 1,000 pCi/L. One run was made with justSr-90, and a second run was made using Sr-90 with calcium, magnesium,and zinc, Experiments #5 and 6, respectively. The third experiment,Experiment #9, was done with the feed containing Sr-90, calcium,magnesium, and zinc. In all three of these experiments, the treated feedconcentration was expected to reach about 50 pCi/L Sr-90. All theseexperiments reached or exceeded that goal. Experiments #9 reduced theSr-90 concentration in the feed to <8 pCi/L.

High Concentration Experiments

Two experiments, #7 and 8, were done using a starting feed concentrationof about 27,941 pCi/L Sr-90. Both experiments were done using a reducedstrip and organic volumes of 0.100 L and 0.500 L, respectively. InExperiment #7, the final Sr-90 concentration in the feed after threehours was 222 pCi/L. The strip Sr-90 concentration was tested afterthree hours and was found to be about 60,000 pCi/L. The concentrationwas expected to be much higher, about 300,000 pCi/L. The lack ofconcentration in the strip was probably due to a significant amount ofthe strip solution trapped in the module from the previous run. Thiseffectively increased the volume of the strip solution, reducing themaximum concentration of Sr-90 achievable in the strip solution. Thistrapped liquid was not purged (which could be done with air purging, ifavailable), and it was present in all of the experiments. Experiment #8added calcium, magnesium, and zinc to the feed in addition to 27,941pCi/L of Sr-90. At the end of five hours, the Sr-90 concentration in thefeed was 84.0 pCi/L, and the strip concentration was 263,382 pCi/L. Thefeed result was better than expected, and the strip result wasacceptable.

One other experiment was run, Experiment #10 using the used organicsolution from Experiments #1, 2, 3, and 4. The strip solution volume wasreduced to 0.040 L, and 0.560 L of the organic solution was used. Theexperiment was run for three hours, and it had a final feed Sr-90concentration of 1,562 pCi/L, reduced from about the initialconcentration of 487,000 pCi/L, and a final strip concentration of1,219,577 pCi/L.

CONCLUSIONS

It has been demonstrated that Sr-90 can be removed from ground watersolutions effectively with the combined supported liquid membrane/stripdispersion process of the present invention. This process was veryeffective to remove Sr-90 from feed solutions containing about 300-1,000pCi/L Sr-90 to the target concentration of less than 8 pCi/L in thetreated feed solutions. Especially, this target concentration was alsoachieved from a ground water solution containing about 1,000 pCi/LSr-90, 80 ppm calcium, 20 ppm magnesium, and 50 ppm zinc. The feedsolutions used containing these ions simulated the ground waters atBrookhaven National Laboratory and West Valley, N.Y.

Two strip solutions were generated with Sr-90 concentrations above250,000 pCi/L. The first was generated from a feed solution of 27,941pCi/L and resulted in a Sr-90 strip concentration of 263,382 pCi/L. Thesecond was generated from a feed solution of about 497,000 pCi/L andresulted in a Sr-90 strip concentration of 1,216,577 pCi/L.

The new extractant, C20 ODPPA, was very effective for the removal ofSr-90, and it gave consistent results below 8 pCi/L Sr-90 in the treatedfeed solutions. The treated feed and used strip solution samples thatwere analyzed did not have any problems while filtering and did not haveany cloudiness, indicating insignificant solubility of this extractantin the aqueous feed and strip solutions.

TABLE 22 Strontium-90 Testing Results Sample Sr-90 k⁺⁺ Time size conc.*Sr-90 Run Sample min g pCi/L cm/s 1 Feed 120 257.6 3.30 7.94E-05 2 Feed120 261.2 3.46 7.83E-05 3 Feed 120 257.4 3.34 9.03E-05 3 Feed 180 251.54.41 — 4 Feed 0 128.2 317 — 4 Feed 240 260.2 4.00 3.78E-05 5 Feed 60124.2 99.4 1.08E-04 32.7 Avg. 66.0** 5 Feed 120 125.6 110 — 64.6 146Avg. 107**  6 Feed 240 247.3 5.52 4.83E-05 7 Feed 0 127.9 27,941 — 7Feed 60 119.5 1,171 1.18E-04 7 Feed 120 125.3 352 4.18E-05 7 Feed 180121.3 222 1.48E-05 8 Feed 300 129.7 84.0 4.61E-05 8 Strip 300 135.2263,382 — 9 Feed 360 1024.5 0.979 4.58E-05 10  Feed 180 120.6 1,5623.81E-05 10  Strip 180 1 1,219,577 — *Strontium 90 concentrationcorrected for 97% removal efficiency of the filters and Y-90 in-growthas a function of time from the preparation of the filtered sample to theradioactivity counting analysis. **Average of the shown analyses ⁺⁺Masstransfer coefficients were calculated using 317 pCi/L, 1,000 pCi/L,27,941 pCi/L and 487,000 pCi/L feed concentrations for the respectiveexperiments.

Example 11

2-Butyl-1-octyl (C12) phenylphosphonic acid (BOPPA) was synthesized bythe following reaction. A solution of 45 g of 2-butyl-1-octanol in 100ml of pyridine was prepared. A solution of 51 g of phenylphosphonyldichloride in 100 ml of pyridine was also prepared. The2-butyl-1-octanol solution was added dropwise to the phenyl phosphonyldichloride solution at a temperature between 5 and 10° C. over a periodof 30 minutes. The reaction was then allowed to continue at the sametemperature for an additional hour while the mixture was stirred. Then,300 ml of concentrated HCl and about 200 g of ice were added to thereaction mixture, resulting in a solution having a pH of 1. The BOPPAwas then extracted from the reaction mixture with 200 ml of toluene. TheBOPPA/toluene solution was washed with 200 ml of 1 M HCl solution anddried with MgSO₄ to produce a clear solution. BOPPA (60 g) was obtainedby evaporating the toluene at 60° C. for 30 minutes.

Example 12

BOPPA was also synthesized by the following reaction (with differentreactant amounts from those used in Example 11). A solution of 31.5 g of2-butyl-1-octanol in 70 ml of pyridine was prepared. A solution of 44 gof phenylphosphonyl dichloride in 70 ml of pyridine was also prepared.The 2-butyl-1-octanol solution was added dropwise to the phenylphosphonyl dichloride solution at a temperature between 5 and 10° C.over a period of 30 minutes. The reaction was then allowed to continueat the same temperature for an additional 4-8 hours while the mixturewas stirred. Then, 200 ml of concentrated HCl and about 200 g of icewere added to the reaction mixture, resulting in a solution having a pHof approximately 1. The mixture was allowed to stir for 24 hours. TheBOPPA was then extracted from the reaction mixture with 200 ml oftoluene. The BOPPA/toluene solution was washed with 200 ml of 1 M HClsolution and dried with MgSO₄ to produce a clear solution. BOPPA at ayield of about 90% based on the alcohol reactant was obtained byevaporating the toluene at 80° C. for approximately 30 minutes.

Example 13

2-Hexyl-1-decyl phenylphosphonic acid (C16 HDPPA) was synthesized by theuse of the same procedure described in Example 12 except 41 g of2-hexyl-1-decanol was used instead of 31.5 g, of 2-butyl-1-octanol.

Example 14

2-Octyl-1-decyl/2-hexyl-1-dodecyl phenylphosphonic acid (C18ODPPA/HDPPA) was synthesized by the use of the same procedure describedin Example 12 except 45.7 g of a mixture of 2-octyl-1-decanol and2-hexyl-1-dodecanol was used instead of 31.5 g of 2-butyl-1-octanol.

Example 15

2-Octyl-1-dodecyl phenylphosphonic acid (C20 ODPPA) was synthesized bythe use of the same procedure described in Example 12 except 50.5 g of2-octyl-1-dodecanol was used instead of 31.5 g, of 2-butyl-1-octanol.

What is claimed is:
 1. A combined supported liquid membrane (SLM)/stripdispersion process for the removal and recovery of one or moreradionuclides or one or more metals from a feed solution containing theradionuclides comprising (1) treating a feed solution containing one ormore radionuclides or one or more metals by passing the feed solution onone side of the SLM embedded in a microporous support material andremoving the radionuclides by the use of a strip dispersion on the otherside of the SLM, the strip dispersion being formed by dispersing anaqueous strip solution in an organic liquid comprising an extractantusing a mixer; and (2) allowing the strip dispersion or a part of thestrip dispersion to separate into two phases, the organic liquid phaseand the aqueous strip solution phase containing a concentratedradionuclide or metal solution.
 2. The process of claim 1 wherein theradionuclide is selected from the group consisting of strontium, cesium,technetium, uranium, boron, plutonium, cobalt, americium, and mixturesthereof.
 3. The process of claim 1 wherein the feed solution is treatedto remove strontium to a concentration of 8 pico Curie per liter (8pCi/L) or lower.
 4. The process of claim 1 wherein the metal is selectedfrom the group consisting of calcium, magnesium, zinc, and mixturesthereof.
 5. The process of claim 1 wherein the aqueous strip solution ofthe strip dispersion comprises an acid.
 6. The process of claim 5wherein the acid is selected from the group consisting of sulfuric acid,hydrochloric acid, nitric acid, acetic acid, and mixtures thereof. 7.The process of claim 1 wherein the organic liquid of the stripdispersion further comprises a modifier in a hydrocarbon solvent ormixtures thereof.
 8. The process of claim 1 wherein the organic liquidof the strip dispersion comprises about 2 wt. % to about 100 wt. %extractant and about 0 wt. % to about 20 wt. % modifier in a hydrocarbonsolvent or mixtures thereof.
 9. The process of claim 8 wherein theorganic liquid of the strip dispersion comprises about 5 wt. % to about40 wt. % extractant and about 1 wt. % to about 10 wt. % modifier in ahydrocarbon solvent or mixtures thereof.
 10. The process of claim 7wherein the modifier is selected from the group consisting of alcohols,nitrophenyl alkyl ethers, trialkyl phosphates, and mixtures thereof. 11.The process of claim 10 wherein the alcohol is selected from the groupconsisting of hexanol, heptanol, octanol, nonanol, decanol, undecanol,dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol,heptadacanol, octadecanol, and mixtures thereof.
 12. The process ofclaim 10 wherein the nitrophenyl alkyl ether is selected from the groupconsisting of o-nitrophenyl octyl ether (o-NPOE), o-nitrophenyl heptylether, o-nitrophenyl hexyl ether, o-nitrophenyl pentyl ether (o-NPPE),o-nitrophenyl butyl ether, o-nitrophenyl propyl ether, and mixturesthereof.
 13. The process of claim 10 wherein the trialkyl phosphate isselected from the group consisting of tributyl phosphate,tris(2-ethylhexyl)phosphate, and mixtures thereof.
 14. The process ofclaim 7 wherein the hydrocarbon solvent is selected from a groupconsisting of n-decane; n-undecane; n-dodecane; n-tridecane;n-tetradecane; isodecane; isoundecane; isododecane; isotridecane;isotetradecane; isoparaffinic hydrocarbon solvent having a flash pointof 92° C., a boiling point of 254° C., a viscosity of 3 cp at 25° C.,and a density of 0.791 g/ml at 15.6° C.; and mixtures thereof.
 15. Theprocess of claim 1 wherein the microporous support material is selectedfrom the group consisting of polypropylene, polytetrafluoroethylene,polyethylene, polysulfone, polyethersulfone, polyetheretherketone,polyimide, polyamide, and mixtures thereof.
 16. The process of claim 1wherein the extractant comprises an alkyl phenylphosphonic acid.
 17. Theprocess of claim 16 wherein the alkyl group of the alkylphenylphosphonic acid is paraffinic (saturated) and has from 6 to 26carbon atoms.
 18. The process of claim 16 wherein the alkylphenylphosphonic acid is selected from the group consisting of2-butyl-1-octyl phenylphosphonic acid (BOPPA), 2-hexyl-1-decylphenylphosphonic acid, 2-octyl-1-decyl/2-hexyl-1-dodecylphenylphosphonic acid, 2-octyl-1-dodecyl phenylphosphonic acid, hexylphenylphosphonic acid, heptyl phenylphosphonic acid, octylphenylphosphonic acid, nonyl phenylphosphonic acid, decylphenylphosphonic acid, undecyl phenylphosphonic acid, dodecylphenylphosphonic acid, tridecyl phenylphosphonic acid, tetradecylphenylphosphonic acid, pentadecyl phenylphosphonic acid, hexadecylphenylphosphonic acid, heptadecyl phenylphosphonic acid, octadecylphenylphosphonic acid, nonadecyl phenylphosphonic acid, decadecylphenylphosphonic acid, undecadecyl phenylphosphonic acid, dodecadecylphenylphosphonic acid, tridecadecyl phenylphosphonic acid, tetrdecadecylphenylphosphonic acid, pentadadecyl phenylphosphonic acid, hexadecadecylphenylphosphonic acid, and mixtures thereof.
 19. The process of claim 16wherein the alkyl phenylphosphonic acid is 2-butyl-1-octylphenylphosphonic acid (BOPPA).
 20. The process of claim 16 wherein thealkyl phenylphosphonic acid is 2-hexyl-1-decyl phenylphosphonic acid.21. The process of claim 16 wherein the alkyl phenylphosphonic acid is2-octyl-1-decyl/2-hexyl-1-dodecyl phenylphosphonic acid.
 22. The processof claim 16 wherein the alkyl phenylphosphonic acid is 2-octyl-1-dodecylphenylphosphonic acid.
 23. The process of claim 16 for the removal ofone or more radionuclides.
 24. The process of claim 23 wherein theradionuclide is selected from the group consisting of strontium, cesium,plutonium, cobalt, americium, and mixtures thereof.
 25. The process ofclaim 24 for the removal of strontium.
 26. The process of claim 25wherein alkyl phenylphosphonic acid is 2-butyl-1-octyl phenylphosphonicacid (BOPPA).
 27. The process of claim 25 wherein the alkylphenylphosphonic acid is 2-hexyl-1-decyl phenylphosphonic acid.
 28. Theprocess of claim 25 wherein the alkyl phenylphosphonic acid is2-octyl-1-decyl/2-hexyl-1-dodecyl phenylphosphonic acid.
 29. The processof claim 25 wherein the alkyl phenylphosphonic acid is 2-octyl-1-dodecylphenylphosphonic acid.
 30. The process of claim 16 for the removal ofmetal.
 31. The process of claim 30 wherein the metal is selected fromthe group consisting of calcium, magnesium, zinc, and mixtures thereof.32. The process of claim 31 wherein the alkyl phenylphosphonic acid is2-butyl-1-octyl phenylphosphonic acid.
 33. The process of claim 31wherein the alkyl phenylphosphonic acid is 2-hexyl-1-decylphenylphosphonic acid.
 34. The process of claim 31 wherein the alkylphenylphosphonic acid is 2-octyl-1-decyl/2-hexyl-1-dodecylphenylphosphonic acid.
 35. The process of claim 31 wherein the alkylphenylphosphonic acid is 2-octyl-1-dodecyl phenylphosphonic acid.